Add stylistic set with oblique letterforms to Italic font

[TaigaYamada]

As per the Inter design program, the identity of Inter is "universal workhorse" and "Semi-geometric industrial sans-serif".
One of the great strengths of Inter is the amount of variants it provides, reflecting the above goal to be a universal workhorse.

In this vein, I'd love a more grotesque inspired alternatives for "f" and "e" in italic styles of the upcoming 4.0, much like the design available in the current stable release of Inter (3.19).

This would greatly aid designers that aim for neutral, Grotesque based aesthetics.
There really is no open source grotesque typeface that rivals Inter in terms of the versatility and neutral voice in my opinion, so having this option in Inter would enhance the capability of the font even further.

Here is a quick approximation of the alternatives (right), created by skewing the roman version by 9.4 degrees, as suggested by the Inter design program.

Additional context
There has been some discussion related to this in the Github discussions. However, I understand the departure of italic styles from roman to improve the ability of italics to emphasize. I just think it'll be great if there are more options for those that seek grotesque aesthetics too.

[rsms]

Thanks for taking the time to write down your thoughts. I appreciate it

[cssobral2013]

@TaigaYamada - I join this request by adding a double-storey 'a'.

[rsms]

Renamed issue and merging #586 into this

[VIDEORealism]

As far as I remember, Inter used to have oblique letterforms until 4.0. It would be very great have these back as alternativ glyphs.